LH/hCG and the Receptor: A Single Receptor for Two Ligands

Gonadotropins are glycoprotein hormones that regulate development and reproduction. They are a family of structurally similar hormones likely evolved from a common ancestral encoding gene and achieved relatively high complexity in humans. Two of these molecules are the luteinizing hormone (LH) and the choriogonadotropin (hCG). They are encoded by a common gene cluster and act on the same receptor (LHCGR), however, are produced in primates and specialized for regulating unique physiological functions, such as LH for gametogenesis and hCG for pregnancy. The action of the two hormones is differentiated by LHCGR, which mediates ligand-specific intracellular signals optimized for supporting LH and hCG physiological functions. Since the two hormones are used as drugs for the treatment of infertility, the knowledge of their mode of action should be helpful for interpreting gonadotropin-related pathological conditions and optimizing their clinical treatment.